[GitHub] XD-DENG opened a new pull request #3718: [AIRFLOW-2872] Fix and Refine 'Ad Hoc Query' View

[GitBox <gi...@apache.org>]

XD-DENG opened a new pull request #3718: [AIRFLOW-2872] Fix and Refine 'Ad Hoc Query' View
URL: https://github.com/apache/incubator-airflow/pull/3718
 
 
   
   ### Jira
   
   - [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR"
     - https://issues.apache.org/jira/browse/AIRFLOW-2872
     - In case you are fixing a typo in the documentation you can prepend your commit with \[AIRFLOW-XXX\], code changes always need a Jira issue.
   
   ### Description
   
   - [x] Here are some details about my PR, including screenshots of any UI changes:
   
   - 1. The `.csv` button in `Ad Hoc Query` actually downloads a plain text file, whil it should be a CSV file. Plain text file works too after changing extension to '.csv', but it would be nicer to directly respond with a CSV file.
   This is addressed by changing `mimetype` to `text/csv`.
   
   - 2. Argument `has_data` passed to the template is not used at all in the template `airflow/query.html`. It can be removed in the `self.render()`.
   
   - 3. We should respond with a CSV file only when user opts in for '.csv' AND the data is available ('df' is generated).  Otherwise we will encounter error below:  `UnboundLocalError: local variable 'df' referenced before assignment`.
   
   - 4. `result = df.to_html(...)` should only be invoked when user doesn NOT choose '.csv'. Otherwise it's a waste of resource to invoke `df.to_html()` since the result it returns will not be used if user asks for CSV downloading instead of a html page.
   
   - 5. remove a commented line.
   
   ### Tests
   
   - [ ] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:
   
   ### Commits
   
   - [ ] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
     1. Subject does not end with a period
     1. Subject uses the imperative mood ("add", not "adding")
     1. Body wraps at 72 characters
     1. Body explains "what" and "why", not "how"
   
   ### Documentation
   
   - [ ] In case of new functionality, my PR adds documentation that describes how to use it.
     - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.
   
   ### Code Quality
   
   - [x] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
   

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